Clamping system for rolling mills



June 27, 1967 Filed April 20, 1964 L. DIOLOT CLAMPING SYSTEM FOR ROLLINGMILLS 5 Sheets-Sheet 2 June 27, 1967 L. DIOLOT 3,327,510

CLAMPING SYSTEM FOR ROLLING MILLS Filed April 20, 1964 5 Sheets-Sheet 3FlG,3

United States Patent 3,327,510 CLAMPING SYSTEM FOR ROLLING MILLS LucienDiolot, Neuilly-sur-Seine, France, assiguor to S0- ciete NouvelleSpidem, Paris, France, a corporation of France Filed Apr. 20, 1964, Ser.No. 361,064 Claims priority, application France, Apr. 19, 1963, 932,0916 Claims. ((11. 72-240) This invention relates to a combined clampingmechanism for rolling mills.

In certain types of rolling mills the adjustment of the distance betweenrolls must be carried out extremely quickly. This is the case mostly inreversing mills for manufacturing products having a relatively shortlength at the beginning of the reduction. It is usually essential that,either for reasons of productivity or for metallurgical requirements,the idling time between each pass be reduced as much as possible.

The most commonly used types of such rolling mills are the bloomingmills or the hot strip reversing mills which roll the ingot just heatedand which produce, after a number of passes in both directions, blanksto be cold rolled afterwards. These rolling mills normally work withsignificant separating forces applied to the rolls.

Rolling mills having screw-type clamping systems that are controllableduring the rolling operation are not considered feasible. These clampingdevices have a very low efiiciency of power transmission due to greatmechanical gearing down and thus the power necessitated for theregulation of the position of the rolls submitted to significantseparating forces would require the use of driving motors of prohibitivepower.

The fact that in such conventional rolling mills it is not possible tocontrol the pressure on the rolls once the product is between the rollsinvolves many drawbacks. For instance, it is impossible to straighten astrip that tends to emerge obliquely, a defect commonly known as Sabreblade. In non-reversing mills such defect is corrected by acting upon asingle one of the screws. Further, it is not feasible to makecorrections of thickness during the last passes so as to obtain blankshaving precise thicknesses, which is advantageous for the subsequentcold rolling operations. Also, in case of minor accidents such ascurrent failure or defective adjustment of the rolls resulting in a tooheavy pass causing the main motor to stall, it is impossible to rapidlyunclamp the rolls. Consequently, the rolls remain in pressure contactwith the hot strip for too long which, in most cases, damages the rollsor results in a significant waste of time to restart the rollingprocess.

Devices for turning slowly the adjusting screws or their nuts so as tobring about a slight unclamping, have already been suggested, but theyare heavy, expensive and slow.

A low speed hydromechanical adjustable device for clamping or unclampingduring rolling operation, which can be used in particular to carry outcorrections of thickness or parallelism during relatively thin rollingpasses is known in the prior art. By way of example reference is made toapplicants French Patent No. 1,213,820, issued on Nov. 2, 1959.

The object of the present invention is to provide a reversible rollingmill having a safety device for avoiding the drawbacks mentioned above.

According to the present invention a rolling mill having a conventionalhigh speed mechanical clamping system is provided in combination withthe above noted known hydromechanical device acting as a hydraulicsafety device and as a high speed clamping system capable of regu- ICElating the position of the rolls during the rolling operation.

According to the present invention there is provided a reversing mill,such as a hot strip mill, comprising a high speed mechanical clampingsystem and a low speed hydromechanical clamping device in which anincrease in the separating force of the rolls causes a pressure rise ina hydraulic circuit. This hydraulic circuit includes a pressure detectormeans controlling a quick drain valve thus ensuring the safety of therolling mill by rapidly separating the rolls when irregular stressesoccur, for instance, during crushing passes.

According to a preferred embodiment, the automatic operation of thequick drain valve is carried out by a system comprising a pressuredetector and a torquemeter. The latter is included in the roll drivingsystem. This torquemeter may be of the type associated with a mechanicalelement of the roll driving system or it may be of the type utilizingthe magnitude of the current supplied to the main driving motor of therolling mill. Such torquemeters supply a signal by closing an electriccontact when the maximum safety valve of the torque is exceeded.

Consequently, every time the safety valves of the torque or the pressureare exceeded, the said electric contact first actuates the quickdischarge valve, then, immediately thereafter, effectuates a high speedunclamping of the mechanical clamping system by starting its motor inthe unclamping direction.

It may be necessary to cut off the main driving motor of the rollingmill when abnormal stresses occur. In this case any safety signalprovided by the pressure detector or the torquemeter can be used forcutting off the driving motor and, when required for starting the motorin reverse.

The present invention will now be described with reference to theattached drawing showing as an example a four roll hot reversible millprovided with the improvements according to the invention.

In the drawing:

FIG. 1 is a side elevational view of one reducing stand of rolls withthe adjusting means shown in section;

FIG. 2 is a front elevational view (partially in section) taken alongline 11-11 of FIG. 1; and

FIG. 3 is a diagrammatic view of the control system associated with astand of rolls.

In these figures, 1 and 1a are the working rolls and 2 and 2a are theback-up rolls. The upper part of each of pillars 12-12a is fitted with aconventional high speed mechanical clamping system with nuts 13-1311,screws 14-14a and revolvable bearing discs 15-15a. The screws areactuated through gears 20-200 by common driving motor 21.

The hydromechanical clamping device comprises, as known, elements 3 and3a, each including electric motors 2242a, stepdown gears 23-2312normally with associated worm gear means, screws 44a and a nut deviceadapted to push the long stroke pistons 5-5a into the cylindrical bodies6-6:: of their respective jacks. Adjacent to the base of the rollingmill there are provided jack means comprising cylinders 8-8a adapted toreceive a piston formed by the reduced lower extremity of the supportmeans for the back-up rolls which comprises pistons 9-9a. Thesecylinders are fed by means of pipes or hydraulic conducits 7-7a fromtheir respective jacks 66a.

This hydromechanical clamping device may have a clamping speed of theorder of 48 mm./minute. Both stepdown gears 23 and 23a may beinterconnected through mechanical transmission means 11 which includesan electromagnetic clutch means 10. When it is desired to adjust theparallelism of the oppositely dis- 3 posed mill rolls, both clampingelements 3-311 are disconnected by actuating clutch means 10.

The same result may be achieved without utilization of the transmissionmeans 11, by substituting therefor two electrically synchronized motors,normally fed by a DC. supply.

Both the mechanical clamping system and the hydromechanical clampingdevice need relatively low power motors since no significant force needbe exerted on the rolls before and after the rolling operation. Thehydromechanical clamping system, however, is capable of exertingsignificant pressure on the roll even with low power motors andtherefore can be used during the rolling operation for regulating thethickness of the strip being rolled or for correcting the parallelism ofthe rolls.

During the rolling passes, the roll separating force is continuouslyindicated and controlled by an operator who observes manometers 17-17awhich are connected to connecting pipes 7-7a of the hydromechanicalclamping device. Quick drain valves 16-16a, which may be eitherelectromagnetically or hand operated, are connected to the pipes 7-7aconnecting the jacks 88a and jacks 6-611.

From the point of view of safety, should, for any accidental reason, themaximum separating force specified for the rolling mill be exceeded, orthe torque value supplied by the rolling mill control motor become toohigh, the protective circuit operates as follows:

An electric circuit is closed, either by an electric contact provided inthe manometers 1717a, or by means of an electric contact of thetorquemeter 24 which can be arranged, for instance, on a driving shaft25 between the rolls and the step-down gear associtaed with the rolldriving motor (see FIG. 3). This circuit first causes through aconventional relay 29 the operation of quick drain valves 16 and 16a toreturn through a pipe 28 to a tank 27 the oil contained in pipes 7-7a ofthe hydromechanical clamping means. Pressure in the hydraulictransmission thus drops almost instantaneously. The same electriccircuit controls the high speed opening of the mechanical clampingsystem. Such operation may take place without delay since the rollseparating force has been considerably reduced by the rapid operation ofthe drain valves 1646a.

Should the excess stresses cause the drive motor of the mill to stall,the former may be immediately reversed so as to prevent the hot stripfrom being jammed between the rolls that could cause damage thereto.Similarly if, owing to a current failure, a strip stops under pressurebetween the rolls, manual operation of the drain valves will relieve thepressure, thus reducing to a large extent the damages which could becaused to the rolls by the hot strip jammed between them.

During the last passes, the rolling mill may operate by fully utilizingthe inherent advantages of the hydromechanical clamping device.

It is known that the strip must emerge at the roll exit side in adirection normal to the roll axis so as to remain on an adjacentlydisposed supporting table (not shown) and be in a correct position forsubsequent cold rolling. If the strip tends to emerge obliquely (Sabreblade), the fact that it is possible to carry out a slow adjustment byusing the hydromechanical clamping device, makes possible, as in aconventional cold strip rolling mill, to bring the strip back to acorrect position.

In addition, if the rolling mill is provided with an instrument formeasuring the thickness of the material emerging at the exit endthereof, it is always possible by using the characteristic of thehydromechanical clamping means that permits adjusting during rollingoperation-to carry out accurate adjustment of thickness for the materialduring the last series of passes, and more particularly during theultimate pass.

Finally, in the hot rolling mills, the removal of the back-up rolls-forperiodic inspection thereof-can be easily carried out owing to thehydromechanical clamping device.

As best shown in the lower portion of FIG. 1, there are provideddiametrically opposed, pivotally mounted support means lit-18a which,during operation of the mill, are tilted in an upwardly convergingdirection.

Preparatory to removing the rolls, they are lifted by means of fluidprovided within jacks 8 and 8a. Then the pivotally mounted support means18 and 18a are brought to a vertical position. By decreasing thepressure on jack means 8 and 8a, each set of rolls is led to rest on thepivotally mounted support means through chock tread rollers 19 and 19a,thereupon the rolls are removed in accordance with the usual method.

Although FIGS. 1 and 2 indicate a specific location for the high speedclamping system (upper part of the rolling mill with control onplatform) and for the hydromechanical clamping device with adjustingjacks under the chocks of the lower back-up roll, it is to be understoodthat the location of both clamping devices may be chosen at willaccording to requirements.

It is further noted that the present invention may be used in anyrolling mill such as a hot four high reversing mill, a two high mill,blooming mill as well as a cold mill.

Although only one embodiment of the invention has been depicted anddescribed, it will=be apparent that this embodiment is illustrative innature and that a number of modifications in the apparatus andvariations in its end use may be effected without departing from thespirit or scope of the invention as defined in the appended claims.

I claim:

1. In a rolling mill of the type including a base, at least one upperand one lower working roll each vertically adjustable with respect toone another and between which a strip to be rolled is adapted to pass,means for driving said rolls, the combination comprising, high speedmechanical clamping means adapted to effect a rapid change of clearancebetween said rolls by screw means driven by first motor means, low speedhydromechanical' clamping means including first hydraulic cylinder meansaffixed to said base, short stroke piston means vertically reciprocablein said first cylinder means and supporting said lower roll, secondhydraulic cylinder means reciprocably receiving long stroke piston meansadapted to effect a low speed change of clearance between said rolls bydisplacing said long stroke piston means by second motor means,hydraulic conduit means communicating between said first and said secondhydraulic cylinder means to maintain both said cylinder means underequal hydraulic pressure, said conduit means including pressure sensingmeans and drain valve means, electric control circuit meansinterconnecting at least said pressure sensing means and said drainvalve means to relieve said hydraulic pressure in both said cylindermeans when said pressure exceeds a predetermined safe valve.

2. The combination according to claim 1 including torque sensing meansfor detecting an increase of the torque of said working rolls, saidtorque sensing means connected to said drain valve means through saidelectrical control circuit means to relieve said hydraulic pressure inboth said cylinder means when said torque exceeds a predetermined safevalue.

3. The combination according to claim 2 wherein said high speedmechanical clamping means includes reversible driving means, saidcontrol circuit means being connected to said driving means foractuating the same when either of said sensing means energizes saidcircuit means.

4. The combination according to claim 1 wherein said high speedmechanical clamping means includes reversible driving means, saidcontrol circuit means being connected to said driving means foractuating the same when said pressure sensing means energizes saidcircuit means.

5. The combination according to claim 3 including a References Citedreversible roll driving means, said control circuit means UNITED STATESPATENTS being connected to said roll driving means for revers- 2 903 9269/1959 Reichl ing the same when either of said sensing means energizes2:985:042 5/1961 Talbot illitj: Sald 3,191,408 6/1965 Bayan 72 245 6.The combmatron accordmg to claim 1 Wherem said drain valve meansincludes manual control means for FOREIGN PATENTS releasing saidpressure to cause separation of .the Working 9 ,1 4/196 r at B itain.

rolls upon failure in current supply means associated With saidelectrical control circuit and said means for 10 CHARLES LANHAM Prlma'yExamine driving said rolls. A. RUDERMAN, Assistant Examiner.

1. IN A ROLLING MILL OF THE TYPE INCLUDING A BASE, AT LEAST ONE UPPER AND ONE LOWER WORKING ROLL EACH VERTICALLY ADJUSTABLE WITH RESPECT TO ONE ANOTHER AND BETWEEN WHICH A STRIP TO BE ROLLED IS ADAPTED TO PASS, MEANS FOR DRIVING SAID ROLLS, THE COMBINATION COMPRISING, HIGH SPEED MECHANICAL CLAMPING MEANS ADAPTED TO EFFECT A RAPID CHANGE OF CLEARANCE BETWEEN SAID ROLLS BY SCREW MEANS DRIVEN BY FIRST MOTOR MEANS, LOW SPEED HYDROMECHANICAL CLAMPING MEANS INCLUDING FIRST HYDRAULIC CYLINDER MEANS AFFIXED TO SAID BASE, SHORT PISTON MEANS VERTICALLY RECIPROCABLE IN SAID FIRST CYLINDER MEANS AND SUPPORTING SAID LOWER ROLL, SECOND HYDRAULIC CYLINDER MEANS RECIPROCABLY RECEIVING LONG STROKE PISTON MEANS ADAPTED TO EFFECT A LOW SPEED CHANGE OF CLEARANCE BETWEEN SAID ROLLS BY DISPLACING SAID LONG STROKE PISTON MEANS BY SECOND MOTOR MEANS HYDRAULIC CONDUIT MEANS COMMUNICATING BETWEEN SAID FIRST AND SAID SECOND HYDRAULIC CYLINDER MEANS TO MAINTAIN BOTH SAID CYLINDER MEANS UNDER EQUAL HYDRAULIC PRESSURE, SAID CONDUIT MEANS INCLUDING PRESSURE SENSING MEANS AND DRAIN VALVE MEANS, ELECTRIC CONTROL CIRCUIT MEANS INTERCONNECTING AT LEAST SAID PRESSURE SENSING MEANS AND SAID DRAIN VALVE MEANS TO RELIEVE SAID HYDRAULIC PRESSURE IN BOTH SAID CYLINDER MEANS WHEN SAID PRESSURE EXCEEDS A PREDETERMINED SAFE VALVE. 